[Mesorah] FW: Psalm 145, Zecher vs. Zeicher

[Sholom Simon]

OK, wading into waters way above my head here:

> MB recommends repeating Zeicher./Zecher davka at parshas Zachor due to
> it's being a safeik d'oraisso

Two basic questions on that -- (without looking at M"B, as I don't have
one at the office here);

1.  If one says "zeicher zecher", isn't that generally halachicly treated
as though one is correcting himself, and it's treated as if you only said
the second word?

2.  What's the d'oraissa here?  Sure, it's d'oraissa to "remember Amalek",
but is the particular method in which we remember Amalek d'oraissa?  (And
if the chiyuv to remember only once per year, and we have two other
readings which mention Amalek...).

(Apologies if these are naive beginner questions)

-- Sholom